1. Field of the Invention
This invention relates to apparatus to provide practice in ball games; in particular, this invention relates to devices to propel tennis balls to players trying to improve their game.
2. State of the Art
Games that involve balls frequently require that athletes playing those games have expertise and coordination with the balls used for that game. It is difficult to achieve the needed degree of expertise and coordination in normal practice with human opponents because humans tire and are not consistent in their throws or serves and the like. Moreover, the players at the higher leaves cannot find challenging enough practice players to improve their own play. This is especially true in the case of the higher end versions of the sports, for example, professional and college or Olympic levels of amateur sports. Therefore, a variety of devices that aid in the practice of handling the balls are in use.
The variety of devices known and patented for propelling balls for practice include, U.S. Pat. No. 3,794,001, issued Feb. 26, 1074, which teaches a device that propels tennis balls from two opposed wheels, one of which is driven the other has a braking mechanism to provide some degree of spin in the vertical plane.
Similarly, U.S. Pat. No. 4,325,351, issued Apr. 20, 1982 teaches a device that has two driven wheels and a nozzle to aim the ball emerging therefrom.
U.S. Pat. No. 4,442,823, issued Apr. 17, 1984, teaches a three-wheel pitching machine. The wheel frame is particularly robust, and effectively hides the operation from the sight of the user.
U.S. Pat. No. 4,712,534, issued Dec. 15, 1987, teaches a two-opposing-wheel ball throwing machine.
U.S. Pat. No. 4,841,945, issued Jun. 27, 1989, teaches a device specific for tennis having two driven wheels and a tall frame. The device features a complex ball delivery device to feed the driving wheels.
U.S. Pat. No. 5,649,523, issued Jul. 22, 1997, teaches a device having three driven wheels to propel a ball. The driving wheels are pivotally mounted allowing them to sweep in a vertical direction, while the ball feeder mechanism is firmly mounted on a fixed frame.
Finally, U.S. Pat. No. 5,865,161, issued Feb. 2, 1999, teaches another approach to the mounting of three wheels to provide a means to propel balls fast and with spin. It includes a tall frame that does not allow easy movement of the ball throwing head of the apparatus.
It can be seen that tennis is a game where practice devices are frequently used. The problems that impede the design of such devices can be seen from the prior art and its attempts to solve the problems. One is serving the balls fast enough to be a realistic mimic of balls that are served at the highest levels of competitive tennis. Another is the problem of allowing ready aiming of the ball while simultaneously serving the balls. And finally, there is the problem of imparting spin to the tennis balls in all directions, to allow top spin, bottom spin, and left and right spin. These devices can allow the balls to be propelled over the net for the player to practice hitting back, either for practice serves or for practicing volleys. Most of these devices now known are set on the ground. Recently some of the devices have placed the ball propulsion device higher for more realistic serves, but it can be seen that the propelling heads are frequently not readily movable. Moreover, feeding the balls to the propelling head is a cumbersome and tricky problem.
Therefore, more realistic and accurate serving devices, allowing the ball to be served faster, higher in the air, at more angles of attack, and at a variety of angels that are readily changeable during practice, while imparting spin in any direction to the ball, would be of great benefit to those practicing the game of tennis.